The present invention relates generally to electronic fuel injection, and specifically it relates to an electromechanical control device for generating a signal related both to the volume of air inducted per cylinder cycle and the speed of the engine.
In an electronically fuel injected internal combustion engine, a predetermined number of control pulses, usually one pulse, is generated per engine revolution to activate the injection valve to supply fuel needed to provide combustion for each cylinder cycle at a desired air fuel ratio. To operate the engine at the desired air fuel ratio, it is necessary to precisely relate the amount of fuel to be injected to the volume of air contributing to the complete combustion of the fuel under all engine operating conditions. Engine operating parameters such as engine speed and intake air speed are sensed as intelligence to control the engine's air fuel ratio at the stoichiometric value. To obtain a control signal, the sensed value of engine speed is divided by the sensed value of intake air. This is conventionally achieved by feeding the sensed voltages to an electronic dividing circuit. However, engine speed tends to increase as much as four times its minimum value while the intake air volume tends to increase as much as ten times its mimimum value. Therefore, the use of the electronic dividing circuit requires a costly complicated circuitry if an accurate computation result is desired.